The present invention relates generally to irrigation systems. More particularly, the present invention relates to an intelligent irrigation rain sensor for use with an advanced irrigation controller and water management system.
Water is a precious resource in our environment. Growing populations, urban and suburban sprawl and ongoing droughts are impacting our water resources, resulting in natural habitat degradation and impacting the amount of water that is available for everyday use. Communities all over the United States have been faced with increased demands on existing water supplies. Recently, with the increasing need for conserving water and mandated water use restriction, there is a greater focus on water conservation, but not just in times of drought. One area that is heavily regulated is in the area of irrigation, especially lawn and landscape. The amount of water relegated to lawn and landscape irrigation, as well as the duration and times that watering is permissible, are being tightly scrutinized by local communities.
Irrigation controllers are well known and have been long used to compensate for rainfall deficits by scheduling and controlling an amount of water allocated to irrigation. Most common types of irrigation controllers incorporate a programmable clock for scheduling the day and time for initiating an irrigation cycle and a timer for programming the duration of a scheduled irrigation cycle. Typically, the clock and timer will allow the operator to separately program irrigation zones under the control of the irrigation controller. The operator sets an irrigation schedule based on, for instance, authorized watering days for the community or neighborhood, and then allocates a watering duration for each irrigation zone. The controller remains in essentially an idle state until the appointed irrigation day and time, wherein the controller commences the irrigation watering routine. These types of controllers are inherently inefficient because the irrigation cycle will commence on the appointed day regardless of the water needs of the landscape. Since the irrigation cycles are programmed in advance, the operator cannot know for sure that the landscape will require irrigating on a day scheduled for irrigation, for instance, it may have recently rained.
Recently, many municipalities have recognized the inefficiencies in preprogramming irrigation cycles and have promulgated codes requiring the use of rain sensors to postpone or cancel irrigation cycles that are scheduled immediately subsequent to or during rainfall. The need to suspend a watering cycle due to the occurrence of an environmental influence is crucial in order to save natural resources, money, and to prevent unsafe conditions. While this measure is a step in the right direction, conventional rain sensors do little more than detect moisture and suspend the pending irrigation cycles until the rain sensor no longer detects moisture.
Prior art rain sensors rely on a hygroscopic material that expands upon contact with moisture from water vapor, rain, snow, or ice. The hygroscopic material is physically connected to a switch that activates when the hygroscopic material expands, sending a signal to the irrigation controller to suspend the irrigation cycle. Once the moisture in the hygroscopic material evaporates, it shrinks and the switch is deactivated, which sends a signal to the irrigation controller to enable the irrigation cycle. The amount of water that the hygroscopic material will absorb is limited by the physical configuration of the material. Sensors that employ smaller quantities of hygroscopic material tend to react quicker to rain, sensing rain immediately and sending a signal to the irrigation controller. The amount of rainfall cannot be accurately determined from this type of sensor. Using more hygroscopic material may give a better rainfall guesstiment, but the accuracy of the sensor is still limited by the amount of water that the material can hold. Moreover, responsiveness is often sacrificed for accuracy, that is while a rain sensor that utilizes a greater quantity of hygroscopic material may be marginally more accurate, it may be less responsive, leading to the lawn sprinklers activating in a rainstorm. Because delays in the irrigation cycle are totally dependent on the rate of evaporation of the water in the hygroscopic material, some irrigation controllers employ watering delay algorithms that further retard the watering cycle, sometimes based on the elapsed time between the deactivate and activate signals from the rain sensor. However, since the estimate is totally reliant on the hygroscopic material of the rain sensor, any estimate of rainfall incorporates some amount of guesswork.